D-Bus Phase 3/4: upgrade sessiond, services, add StatusNotifierWatcher, consolidate configs

- redbear-sessiond: add Manager.Inhibit (pipe FD), CanPowerOff/CanReboot/
  CanSuspend/CanHibernate/CanHybridSleep/CanSleep (return na), PowerOff/
  Reboot/Suspend stubs, GetSessionByPID, ListUsers, ListSeats,
  ListInhibitors, ActivateSession/LockSession/UnlockSession/TerminateSession
- redbear-sessiond: add Session SetIdleHint, SetLockedHint, SetType,
  Terminate methods; wire PauseDevice/ResumeDevice/Lock/Unlock signal
  emission via SignalEmitter injection; add dynamic device enumeration
  scanning /scheme/drm/card* and /dev/input/event* at startup
- redbear-sessiond: replace infinite pending() with stoppable shutdown
  via tokio watch channel + control socket shutdown command
- redbear-upower: add Changed signal emission with 30s periodic polling
  and power state snapshot comparison
- redbear-notifications: add ActionInvoked signal, expand capabilities
  to body + body-markup + actions
- redbear-polkit, redbear-udisks: replace pending() with stoppable
  shutdown via signal handling + watch channel
- Add redbear-statusnotifierwatcher: new session bus service implementing
  org.freedesktop.StatusNotifierWatcher for KDE system tray
- Add D-Bus activation file for StatusNotifierWatcher
- KWin session.cpp: try LogindSession before NoopSession fallback
- Consolidate config profiles: remove obsolete redbear-desktop, redbear-kde,
  redbear-live-*, redbear-minimal-*, redbear-wayland configs; simplify
  to three supported targets (redbear-full, redbear-mini, redbear-grub)
- Update DBUS-INTEGRATION-PLAN.md and DESKTOP-STACK-CURRENT-STATUS.md
  with Phase 3/4 fragility assessment, KWin readiness matrix, and
  completeness gap analysis

local/docs/GRUB-INTEGRATION-PLAN.md

@@ -3,8 +3,8 @@
 **Date:** 2026-04-17
 **Status:** Fully implemented (build-tested, not yet runtime boot-tested). ESP formatted as FAT32
 per UEFI spec. Both Phase 1 (post-build script) and Phase 2 (installer-native) are wired.
-**Remaining:** Runtime UEFI boot validation in QEMU (`make all CONFIG_NAME=redbear-full-grub && make qemu`).
-**Prerequisite:** The `grub` package is included in `redbear-full-grub.toml` for clean-tree builds.
+**Remaining:** Runtime UEFI boot validation in QEMU (`make all CONFIG_NAME=redbear-grub && make qemu`).
+**Prerequisite:** The `grub` package is included in `redbear-grub.toml` for clean-tree builds.
 **Approach:** Option A — GRUB as boot manager, chainloading Redox bootloader
 
 ## Overview
@@ -257,7 +257,7 @@ ESP layout automatically.
 ### Config Usage
 
 ```toml
-# config/redbear-full-grub.toml
+# config/redbear-grub.toml
 include = ["redbear-full.toml"]
 
 [general]
@@ -271,7 +271,7 @@ Or via CLI (note: INSTALLER_OPTS replaces defaults, so --cookbook=. must be incl
 make all CONFIG_NAME=redbear-full INSTALLER_OPTS="--cookbook=. --bootloader grub"
 ```
 
-**Note:** The config file approach (`redbear-full-grub.toml`) is preferred over the CLI flag
+**Note:** The config file approach (`redbear-grub.toml`) is preferred over the CLI flag
 because INSTALLER_OPTS completely replaces the default value (`--cookbook=.`) rather than
 appending to it. Omitting `--cookbook=.` breaks local package resolution for GRUB.
 
@@ -356,7 +356,7 @@ make qemu
 make r.grub
 
 # Build image with GRUB config (installer fetches GRUB automatically)
-make all CONFIG_NAME=redbear-full-grub
+make all CONFIG_NAME=redbear-grub
 
 # Or via CLI flag
 make all CONFIG_NAME=redbear-full INSTALLER_OPTS="--bootloader grub --cookbook=."
@@ -376,7 +376,7 @@ make qemu
 CI=1 ./target/release/repo cook grub
 
 # Verify host-side installer accepts --bootloader flag
-build/fstools/bin/redox_installer --bootloader=grub --config=config/redbear-full-grub.toml --list-packages
+build/fstools/bin/redox_installer --bootloader=grub --config=config/redbear-grub.toml --list-packages
 
 # Verify fat_tool.py operations
 python3 local/scripts/fat_tool.py --help